The invention relates to a cullet preheater having a heating section in which hot gas coming from a hot gas supply duct can be passed through the cullet, yielding heat to the latter, and can be carried away by a hot gas exhaust duct. Within the preheater the cullet is guided between walls which form a cullet shaft and permit the entry and exit of gas.
Preheating crushed glass as a recyclable raw material (known as "cullet") to aid in the melting of glass by means of hot gas--generally exhaust from glass melting furnaces--is a method which has long been known for the achievement of an optimum energy balance and, as an additional effect, for the achievement of a certain filtering of the exhaust gas in glass production, and it is described for example in the German Pat. No. 21 61 419. This patent also describes an apparatus for preheating cullet by means of exhaust gas from glass melting furnaces. The disclosed apparatus consists essentially of an upright cylinder which is filled with cullet and in which hot gas is introduced through pipe connections in the bottom area and withdrawn at an area further above it. Centrally in the cylinder there is a perforated pipe which serves to guide the flow of the hot gas.
In addition to this apparatus a preheater is known in which cullet is guided in a vertical shaft between two gas-permeable guiding walls. Here hot gas enters the cullet through the one guiding wall, flows transversely through the cullet and exits through the second gas-permeable guiding wall.
It is a disadvantage of both the known preheaters that the condensation of components of the hot gas, mostly sodium bisulfate, causes the individual glass shards to stick or cake up in the cullet preheater, impairing or even totally destroying the free-flowing quality of the cullet. As a result, the heated cullet can be removed from the preheater only with difficulty.
Another disadvantage of the known preheaters is that they can be operated only by one established method, and thus cannot be adapted to varying properties of the cullet that is to be preheated.
The problem therefore arises of heating a preheater of the kind described above, in which the described disadvantages will be avoided and in which a trouble-free flow of the cullet will be assured, along with ease of removal from the preheater.
In further development of the invention, the preheater is to be flexibly adaptable to varying requirements.